Afghan President Hamid Karzai intends to impose rules restricting international involvement in anti-corruption investigations, a move that U.S. officials fear will hobble efforts to address the endemic graft that threatens support for his administration in Afghanistan and the United States.

Karzai wants to circumscribe the role of American and other foreign law enforcement specialists in two key anti-corruption organizations in the Interior Ministry by not allowing them to have direct involvement in investigations.

"The management will be Afghan, and the decision-makers will be Afghan, and the investigators will be Afghan," Mohammad Umer Daudzai, Karzai's chief of staff, said in a telephone interview Wednesday. Foreign advisers, most of whom work for the U.S. Justice Department, will be limited to "training and coaching, but not decision-making," he said.

Concern about Karzai's willingness to root out corruption has emerged as a flashpoint in the U.S.-Afghan relationship, with American officials arguing that he has not done enough to demand accountability and Karzai maintaining that the problem has been fueled by the influx of billions of dollars in foreign assistance.

The planned changes have alarmed U.S. officials in Kabul and Washington and prompted efforts to try to persuade Karzai and his advisers to soften the restrictions.

"What he's proposing would effectively neuter these two bodies," said a U.S. official involved in Afghanistan policy.

Daudzai said Karzai also plans to prevent the U.S. government from influencing the selection and augmenting the salaries of the Afghan investigators and prosecutors who serve in the two groups.

In June, U.S. officials involved in anti-corruption investigations told The Washington Post that senior officials in Karzai's government had derailed investigations of politically connected Afghans. "Above a certain level, people are being very well-protected," one senior U.S. official told The Post.

The latest controversy began with the arrest in late July of Mohammad Zia Salehi, a presidential aide, on charges that he solicited a bribe of $10,000 and a new car to impede an investigation of a money-exchange firm that is alleged to have funneled $3 billion in undeclared cash out of the country. Reports about the firm and the high-level interference with inquiries had prompted Rep. Nita M. Lowey (D-N.Y.), who chairs the House subcommittee responsible for foreign aid, to place a hold on $3.9 billion in U.S. reconstruction funding for Afghanistan.

The case against Salehi was assembled by the Interior Ministry's Major Crimes Task Force and the Special Investigative Unit. Although they are part of the Afghan government, both bodies have received extensive support from a team of U.S. law enforcement advisers in Kabul who work for the FBI, the Drug Enforcement Administration and other arms of the Justice Department.

The advisers have provided vital support to the two Afghan organizations, U.S. officials said, including access to wiretaps and other intelligence data. The U.S. advisers also help the Afghans assemble cases and conduct raids.

U.S. officials insist that the Afghan leaders of the organizations make the final decisions about which cases to pursue and that they have sought to do so without being swayed by political considerations.

But Karzai's advisers think that U.S. officials have de facto control over the groups. "There is suspicion that the international partners have a decision-making role," Daudzai said.

Another U.S. official familiar with the issue said the planned limits on U.S. involvement could have a significant impact on the ability of both bodies to conduct the sort of anti-graft work that the Obama administration deems crucial. Partnership, the official said, has been "an essential feature of these institutions."

Daudzai denied that the changes would impede investigations. He said Karzai "is not against these two units."

"He wants them to exist, and he wants them to be strengthened," Daudzai said. "But he wants them to operate within an Afghan framework."

Karzai has expressed anger at the use of wiretaps to build the case against Salehi - calling it a violation of "human rights principles" - and the decision to arrest him during an early-morning raid of his house. The president has acknowledged intervening to have Salehi released, and since the incident, he has called for a new law to spell out the roles of both organizations.

It is that legislation, being drafted by his Ministry of Justice, that would set the new conditions on foreign involvement. Daudzai said Karzai intends to enact the new rules as soon as they are finished.

In addition to the limits on partnership, the rules will bar direct payments to members of both organizations to increase their salaries. Selection of investigators and prosecutors for both bodies will be made by the Interior Ministry. U.S. officials worry that will allow Karzai and his cronies to choose who serves and to remove anyone targeting the president's family or close associates.

Before Karzai's proposed restrictions were known, senior U.S. civilian and military officials expressed support for his desire to provide a legal framework for the organizations. "One of the legitimate concerns on the part of the Afghan government leadership is that their roles are not spelled out in law, and that needs to take place," Gen. David H. Petraeus, the top U.S. commander in Afghanistan, said last month.

Defense Secretary Robert M. Gates, speaking in Kabul last week after meeting with Karzai, said he supports the Afghan leader's view that anti-corruption investigations should be led by Afghans, but he noted that such inquiries should be credible and internationally accepted.

Daudzai accused officials of "unnecessarily enlarging and politicizing the issue."

"They want us to move toward more self-reliance, to strengthen our sovereignty, and then they don't let us make a decision," he said.